This is a very early Piano. The Piano powers up ok and all function buttons and lights work but there is no sound from the speaker or headphone port. There is no visible damage on the boards and no sign of leaky capacitors etc.
Any help greatly appreciated.
Use an amp and feed AUX signal into it to check if that works. AUX out is before the power amps - speakers and headphones are driven by an STK-465-105 integrated amp chip.
If AUX out does not work either then need to look at the mute circuit (yellow section) and/or volume circuit (blue section) around circuit area below
Thanks for the info. I found several different faults. The power supply boardhad dry solder joints which meant no power to the Amp circuit. Once the initial fault was repaired I had no sound from the speakers. I found 30V on one of the speaker channels which meant the safety relay would not switch. Dry solder joints on the Amp chip were the cause of this. Last of all the master volume control would not work. The potentiometer measured way out of spec. New part on order. 
